Polyvinyl chloride thermoplastic elastomer composition

ABSTRACT

A thermoplastic elastomer composition comprising 100 parts by weight of a vinyl chloride resin, from 20 to 300 parts by weight of a nitrile rubber, from 25 to 200 parts by weight of a plasticizer, from 10 to 200 parts by weight of a filler and a curing agent for the rubber, and being meltable by a roll set at a temperature of 190° C.

This application is a continuation application Ser. No. 07/379,267,filed on Jul. 13, 1989, now abandoned.

The present invention relates to a thermoplastic elastomer compositionof a polyvinyl chloride-nitrile rubber (NBR) system having excellentprocessability, high tensile strength and low compression set and thusbeing useful as a substitute for vulcanized rubber, a process forproducing such an elastomer composition and a molded product of such anelastomer composition. Here, the thermoplastic elastomer means asubstance which exhibits both thermoplasticity and elasticity. Namely,it is a substance which is capable of being molded as a thermoplasticmaterial by a usual molding method for plastics, such as extrusionmolding, injection molding, blow molding or roll calendering and whichat the same time exhibits elasticity like rubber. The thermoplasticelastomer provides a merit such that elasticity can be thereby obtainedwithout necessity of a cumbersome vulcanization step as required in thecase of usual vulcanized rubber.

The vinyl chloride resin is generally excellent in the chemical andphysical properties and provides a soft molded product having a suitableelasticity and excellent flexibility when a plasticizer is incorporatedthereto. As such, it is used in many applications as resin material forvarious molded products such as films, sheets, tubes or containers.

However, molded products of a plasticized vinyl chloride resin havedifficulties such that they have strong creep tendency and largecompression set and thus are poor in the restorability when thecompression force has been removed. For example, a soft molded productobtainable by incorporating a plasticizer to a usual vinyl chlorideresin has a compression set as large as from 60 to 70% as measured inaccordance with JIS K-6301 at 70° C. for 22 hours under a compressionrate of 25% (the same applies hereinafter when the compression set isreferred to). Therefore, its use for the applications where a smallcompression set is required, such as packing, is limited.

In order to reduce the compression set for improvement, it has beenattempted to use such a plasticized vinyl chloride resin in combinationwith a partially cross-linked NBR. For example, such use is disclosed inthe following literatures.

(1) Rubber Age, July, 1973, p.43-47

(2) Rubber World, March, 1973, p.42-50

(3) Rubber Chemistry and Technology, Rubber Reviews for 1978, p.395-397

(4) L'Official des Plastique et du Caoutchauc, Mai, 432-437 (1979)

However, it is hardly possible to reduce the compression set to a levelof less than 40%, although it may be reduced to a level of from 40 to50%, by the above-mentioned methods. The improvement is still inadequateto use the product as a substitute for vulcanized rubber.

If it is attempted to reduce the compression set by increasing theamount of incorporation of the partially cross-linked NBR as a componentto reduce the compression set of a vinyl chloride resin, there will be adrawback that other important properties such as tensile strength,elongation and tear strength tend to deteriorate, although thecompression set may be reduced to a level of about 40%. For example, theresults will be as shown in the following Table 1.

                  TABLE 1                                                         ______________________________________                                        Test No.       1       2      3     4    5                                    ______________________________________                                        PVC (- P = 3000) 100    100    100  100  100                                  Chemigum P8B1-A-2*                                                                             0      30     50   100  150                                  Dioctyl phthalate                                                                              100    100    100  100  100                                  Ba--Zn stabilizer                                                                              3      3      3    3    3                                    Epoxidized soybean oil                                                                         3      3      3    3    3                                    Tensile strength (kg/cm.sup.2)                                                                 120    102    101  83   75                                   Elongation (%)   420    380    350  290  290                                  Compression set (%)                                                                            55     51     46   41   38                                   ______________________________________                                         *Partially precrosslinked NBR manufactured by Good Year Co.              

Accordingly, for a thermoplastic elastomer to be useful as a substitutefor conventional vulcanized rubber, the thermoplastic elastomer isdesired to satisfy both requirements for the mechanical strength and thecompression set.

The present inventors have conducted various studies to obtain apolyvinyl chloride thermoplastic elastomer composition having a lowcompression set and high strength while maintaining the desiredproperties as the thermoplastic elastomer. As a result, they have foundit possible to obtain a thermoplastic elastomer having the compressionset and breaking stress improved while maintaining the thermoplasticityby adding a usual curing agent for rubber to a system comprising a vinylchloride resin, a nitrile rubber, a plasticizer and a filler andreacting the mixture under kneading.

The present invention provides a thermoplastic elastomer compositioncomprising 100 parts by weight of a vinyl chloride resin, from 20 to 300parts by weight of a nitrile rubber, from 25 to 200 parts by weight of aplasticizer, from 10 to 200 parts by weight of a filler and a curingagent for the rubber, and being meltable by a roll set at a temperatureof 190° C.

Now, the present invention will be described in further detail withreference to the preferred embodiments.

In the accompanying drawings:

FIG. 1 is a cross sectional view of a molded glass run channel product.

FIG. 2 is a cross sectional view of the same molded glass run channelproduct put in a casing.

FIG. 3 is a cross sectional view of the same glass run channel productput in a metal casing in which a spacer was inserted.

FIG. 4 is a cross sectional view of the same glass run channel productfrom which the spacer was removed to determine the residual strain.

FIG. 5 is a perspective view of a molded weather stripping product.

FIG. 6 is a cross sectional view of the same molded weather strippingproduct compressed by a device for measuring the compression set.

When the thermoplastic elastomer composition of the present invention iskneaded at a temperature of from 140° to 220° C, preferably from 150° to210° C., the curing agent in the composition reacts with the nitrilerubber to provide a high tensile strength of at least 120 kg/cm² and anexcellent compression set of at most 40% while maintaining thethermoplasticity. From the experimental results shown in Table 2, it isevident that the reason for the improvement of the breaking tensilestress and the compression set while maintaining the processability asthe thermoplastic elastomer by the addition and reaction of the curingagent is that the curing agent scarcely reacts with the PVC componentserving to maintain the plasticity of the composition and reactsexclusively with NBR. Namely, in the case of NBR, the gel contentincreases and the swelling decreases by the addition of the curingagent. This indicates that the cross linking reaction has taken place.Whereas, with PVC, the gel content scarcely increases under suchconditions, thus showing that no substantial reaction has taken place.Thus, it is assumed that with the mixture of PVC and a nitrile rubber,the curing agent predominantly reacts with the nitrile rubber andscarcely reacts with PVC.

                                      TABLE 2                                     __________________________________________________________________________    Test No.    6   7   8   9   10  11  12  13  14                                __________________________________________________________________________    Chemigum P8B1A-2                                                                          100 100 100 --  --  --  --  --  --                                JSR PN-30A  --  --  --  100 100 100 --  --  --                                PVC SH-170  --  --  --  --  --  --  53  53  53                                Dioctyl phthalate                                                                         --  --  --  --  --  --  47  47  47                                (plasticizer)                                                                 Ba--Zn system                                                                             --  --  --  --  --  --  1.6 1.6 1.6                               (stabilizer)                                                                  Epoxidized soybean oil                                                                    --  --  --  --  --  --  1.6 1.6 1.6                               Perhexa 3M-40*                                                                            0   1   2   0   1   2   0   1   2                                 Triallyl    5   5   5   5   5   5   5   5   5                                 isocyanurate**                                                                Gel content (%)                                                                           78.5                                                                              82.3                                                                              85.2                                                                              5.3 81.5                                                                              89.8                                                                              0.1 0.1 0.4                               Swelling    15.4                                                                              10.0                                                                              7.5 --  10.5                                                                              8.5 --  --  --                                __________________________________________________________________________     *Amount of the product of a purity of 40 wt %.                                **Cross linking assistant.                                               

The tests were conducted in the following manner.

Into a Brabender Plastograph having the jacket temperature preliminarilyadjusted to 150° C., 60 g of the blend composition of Test No. 6 , toNo. 14 was charged and kneaded for 10 minutes at a rotational speed of60 rpm to obtain a block or powdery product. The block product therebyobtained was sheeted by rolls, and the sheet was then cut into piecesand dissolved in tetrahydrofuran at a concentration of 0.5%. Whereas,the powder product was in its form dissolved in tetrahydrofuran at aconcentration of 0.5%. The solution was left at room temperature for 20hours under gentle shaking, whereupon the gel content (%) was obtainedfrom the insolubles, and the swelling degree was obtained by dividingthe weight of the swelled state (the state containing tetrahydrofuran)by the weight of the insoluble polymer after drying.

MATERIALS USED

Chemigum P8B1A-2: Partially pre-crosslinked NBR (manufactured by GoodYear Co.)

JSR PN-30: Non-cross-linked NBR (manufactured by Japan Synthetic RubberCo., Ltd.)

PVC SH-170: Vinyl chloride homopolymer having a polymerization degree of1,700 (manufactured by Denki Kagaku Kogyo Kabushiki Kaisha)

Perhexa 3M-40: Peroxide type curing agent,1,1-bis-tert-butylperoxy-3,3,5-trimethylcyclohexane (purity: 40% byweight, manufactured by Nippon Oil and Fats Co., Ltd.)

The vinyl chloride resin to be used for the thermoplastic elastomercomposition of the present invention, may be a usual vinyl chlorideresin, and it is usual to employ a vinyl chloride resin having anaverage degree of polymerization of from 700 to 6,000.

Further, the vinyl chloride resin includes copolymers of vinyl chloridewith the following monomers. Namely, such monomers include, for example,a fatty acid vinyl ester, a vinylidene halide, an alkyl acrylate, analkyl methacrylate, acrylonitrile, an alkylvinyl ether, styrene andderivatives thereof.

NBR useful in the present invention preferably contains from 20 to 45%of bound acrylonitrile, and it may be of a non-cross-linked type or across-linked type.

The composition of the present invention in which a partiallypre-crosslinked type NBR is employed, provides stabilized extrusionprocessability and provides a molded product having a smooth surface. Onthe other hand, the composition in which a non-cross-linked NBR isemployed, provides a large elongation.

The amount of NBR is from 20 to 300 parts by weight relative to 100parts by weight of the vinyl chloride resin. If the amount is less than20% by weight, the effect of reducing the compression set tends to betoo weak. On the other hand, if the amount exceeds 300 parts by weight,the processability tends to be poor. Particularly preferred is an amountwithin a range of from 20 to 200 parts by weight.

As to the plasticizer, there is no particular restriction. Anyplasticizer may be employed so long as it is useful for the productionof a plasticized vinyl chloride resin product. For example, it may be aplasticizer of a phthalic acid ester type, a trimellitic acid estertype, a pyromellitic acid ester type, an aliphatic dibasic acid estertype, a glycol ester type, a fatty acid ester type, a phosphoric acidester type or a citric acid ester type. Further it may be an epoxy typeplasticizer or polyester type plasticizer.

The amount of the plasticizer is from 25 to 200 parts by weight relativeto 100 parts by weight of the vinyl chloride resin. If the amount isless than 25 parts by weight, the processability tends to be poor andthe product tends to be too hard, thus failing to present thecharacteristics as an elastomer. On the-other hand, if it exceeds 200parts by weight, the physical properties tend to deteriorate to apractically useless level.

As the curing agent, any curing agent useful for curing (or vulcanizing)rubber, may be employed.

A suitable curing agent system includes a sulfur + vulcanizationaccelerator system, and a system using a peroxide, an azide, a maleimideor a phenol resin as the base.

Specific examples of the curing agent include sulfur, zinc oxide,magnesium oxide, an organic peroxide, triazinethiol, a benzothiazolesulfenamide accelerator, benzothiazyl disulfide, a phenol resin,m-phenylene bismaleimide, thiuram disulfide and dipentamethylene thiuramhexasulfide.

Preferred organic peroxide curing agents include, for example, laurylperoxide, benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumylperoxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 1,1-bis(tert-butylperoxy)-2,3,5-trimethylcyclohexane,tris-α,α-dimethyl-α-(tert-butylperoxy)methylbenzene,αα-bis(butylperoxy)diisopropylbenzene,bis(4-tertbutylcyclohexyl)peroxydicarbonate and tert-butyl perbenzoate.

Further, preferred phenol resin curing agents include, for example, areactive type alkyl phenolformaldehyde resin and a reactive typebrominated alkylphenol-formaldehyde resin, specifically TACKIROL 201 andTACKIROL 250 (both manufactured by Sumitomo Chemical Co., Ltd.),respectively.

As an accelerator, an aldehyde ammonia, an aldehyde amine, guanidine, athiourea, a thiazole, a dithiocarbamic acid salt, a xanthogenic acidsalt or a thiuram, may be used.

Further, as a curing assistant, dibenzo-p-quinonedioxime,p-quinonedioxime, p-phenylenebismaleimide, a trialkyl cyanurate,ethylene glycol dimethacrylate, pentaerythritol triacrylate,trimethylolpropane triacrylate or neopentylglycol diacrylate may beemployed.

The amount of the curing agent varies depending upon the type of thecuring agent and the combination with an accelerator, but is usually atleast 0.1 part by weight relative to 100 parts by weight of the totalamount of the vinyl chloride resin and NBR.

As the filler, carbon black, calcium carbonate, titanium oxide, talc,asbestos, aluminum hydroxide, magnesium hydroxide, clay, silica, whitecarbon, etc. may be used in an amount of from 10 to 200 parts by weightresin. If the amount of the filler is less than 10 parts or more than200 parts, the physical properties of the product tend to deteriorate.

Further, other additives such as a heat stabilizer, a lubricant, aprocessing assistant, a pigment and a flame retardant, may beincorporated in a proper amount, as the case requires.

The heat stabilizer includes, for example, a lead type heat stabilizersuch as tribasic lead sulfate, a tin type stabilizer such as dibutyltinmaleate and a metal soap such as zinc stearate or calcium stearate, andit is used in a suitable amount as the case requires.

The pigment includes, for example, color carbon black, chrome yellow,titanium oxide and phthalocyanine green, and it is used in a suitableamount as the case requires.

The processing assistant may be the one commonly used for a vinylchloride resin, such as a low molecular weight polyethylene or a higherfatty acid ester.

To the elastomer composition of the present invention, other plastics orrubbers may be incorporated for modification as the case requires. Forexample, a polyurethane, an acrylate resin, a methacrylate resin, an ABSresin, a MBS resin, a nylon resin, polychloroprene, EPDM and modifiedEPDM may be mentioned.

The thermoplastic elastomer composition of the present invention can beprepared by kneading the above-mentioned various components by means ofa kneader which is commonly used for kneading a plasticized vinylchloride resin blend, such as an open roll mill, a kneader of closedsystem such as a Banbury mixer, a pressure kneader or an intensivemixer, a usual single screw extruder, a twin screw extruder, acokneader, an extruder having two screws rotating in the same direction(TEM manufactured by Toshiba Kikai K.K. or PCM manufactured by IkegaiTekko K.K.), a kneader rudder type high speed agitation extruder (FCMmanufactured by Kobe Steel Ltd.), Plastifikator, manufactured by Wenerand Pfleiderner, West Germany, or Plasticator, manufactured by IkkiSeisakusho, which is a kneading extruder comprising a conical rotorhaving a plurality of grooves on its surface and a barrel having arecess well corresponding to the outer shape of the rotor and having aplurality of grooves on the surface of the recess well, a KCK continuouskneading extruder manufactured by Kabushiki Kaisha KCK, which is akneading extruder comprising an extruder screw having a plurality ofcollar blades and a barrel having an internal shape corresponding to theouter shape of the screw, or a Brabender mixer. Among these kneaders, aclosed system kneader is preferred since the kneading time can therebyfreely be selected, and the extruder having twin screws rotating in thesame direction, Plastifikator, Plastikator and the KCK continuouskneading extruder are preferably employed in view of their excellentkneading effects.

Kneading is conducted usually by adjusting the jacket temperature, therotational speed and the kneading time so that the temperature of theblend composition itself will be at a level of from 140° to 220° C.,preferably from 150° to 210° C. As opposed to the kneading in theinitial stage for the preparation of a usual vulcanized rubber whereinthe temperature of the blend composition is maintained at a level of nothigher than about 120° C. to suppress the reaction of the curing agent,according to the present invention, kneading is conducted at a hightemperature suitable for the particular curing agent used, within arange of from 140° to 220° C., preferably from 150° to 210° C., in orderto let the reaction of the curing agent proceed during the kneading.

If the temperature of the blend composition to be kneaded is less than140° C., the reaction of the curing agent tends to proceed inadequately.On the other hand, if the temperature exceeds 220° C., the compositiontends to undergo thermal decomposition. In each case, desired moldingcomposition tends to be hardly obtained.

For molding the thermoplastic elastomer composition of the presentinvention, a molding machine commonly used for molding a usual resinmaterial may be employed such as an extrusion molding machine, aninjection molding machine, a calender molding machine or a compressionmolding machine. Accordingly, a desired molded product can be obtainedwithout requiring a time-consuming vulcanization step commonly requiredfor a usual vulcanizate. Further, as opposed to the case of vulcanizedrubber, defective products or non-useful portions of molded productssuch as sprue runner portions formed during the molding of thecomposition of the present invention, may be reused together with thesame composition or together with other thermoplastic resins formolding, if necessary, after being treated by e.g. pulverizationtreatment.

For the kneading by means of such a kneader, a part or whole of thestarting materials may preliminarily be blended by a separate Henschelmixer or ribbon blender before supplying it to the kneader, or thestarting material may directly be supplied to the kneader withoutconducting such preliminarily blending. Otherwise, a part of materialsmay preliminary be pelletized before supplying to the kneader.

The starting material NBR may be in a block form or in a powder form.

By virtue of the excellent creep resistance, the dimensional stabilityat high temperatures, the low compression set and the high mechanicalstrength, the molded product of the composition of the present inventionis useful for various applications for which conventional vulcanizedrubber is employed, and the shape of the molded product is not limited,so that it is useful for various applications in a wide range of fieldssuch as industrial, automobile and building fields, for example, forpackings, gaskets, sheets, hoses, tubes, rolls, grips, grommets, glasschannels, weather strips, mud-guards, dust boots, various containers andcushions.

The molded product of the present invention can be produced withoutrequiring a cumbersome vulcanization step as required for rubber and canbe readily provided by a molding method similar to the one forthermoplastic materials.

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted to such specific Examples.

    ______________________________________                                        Vinyl chloride resin having an                                                                      100    parts by weight                                  average degree of polymerization                                                                           (1 kg)                                           of 1700 (Denka vinyl SH-170,                                                  manufactured by Denki Kagaku                                                  Kogyo Kabushiki Kaisha)                                                       Ba--Zn fatty acid salt composite                                                                    3      parts by weight                                  stabilizer (BZ-100J, manufactured                                             by Katsuta Kako K.K.)                                                         Epoxidized soybean oil                                                                              3      parts by weight                                  (Adekacizer O-130P, manufactured                                              by Adeka Argus Chemical Co.)                                                  Calcium carbonate (NS-400,                                                                          50     parts by weight                                  manufactured by Nitto Funka                                                   Kogyo K.K.)                                                                   Sulfur                1.5    parts by weight                                  Tetramethylthiuran disulfide                                                                        1      part by weight                                   (Nocceler CZ, manufactured by                                                 Ouchi Shinko K.K.)                                                            Zinc oxide            5      parts by weight                                  Partially pre-crosslinked powdery                                                                   50     parts by weight                                  NBR (Chemigum P8B1A2, manufacture                                             by Good Year Co.)                                                             Di-2-ethylhexyl phthalate (DOP)                                                                     90     parts by weight                                  ______________________________________                                    

The above components were charged into a pressure kneader manufacturedby Moriyama Seisakusho with a jacket temperature of 150° C. and kneadedfor 10 minutes at a fore roll rotational speed of 51 rpm and at a rearroll rotational speed of 34 rpm, whereupon the temperature of the resincomposition was 175° C. The respective components were added in theabove identified parts by weight relative to 100 parts by weight (1 kg)of the vinyl chloride resin. The total amount of the components wasabout 3 kg.

The composition thus obtained was kneaded by 12 inch twin rolls presetat a surface temperature of 180° C. for 10 minutes to obtain a sheet,which was press-molded to obtain test pieces, which were then subjectedto a tensile strength test, a tear strength test and a compression settest. Further, a part of the sheet was subjected to a sheet pelletizerto obtain angular pellets, which were used for flexible contourextrusion, whereby the processability was evaluated from the outerappearance of the extruded product. The results are shown in Table 4.

COMPARATIVE EXAMPLE 1

The operation was conducted in the same manner as in Example 1 exceptthat sulfur and Nocceler CZ were not used.

EXAMPLES 2 to 6

The operation was conducted in the same manner as in Example 1 exceptthat the blend composition was as identified in Table 4.

EXAMPLE 7

The operation was conducted in the same manner as in Example 1 exceptthat instead of the pressure kneader of closed system used in Example 1,a 75 l Henschel mixer of open system was employed, and NBR was not addedat the initial stage and was added after the mixture was dried up byhigh speed rotation to a free-flowing powder, followed by gentleagitation.

The powdery blend composition thus obtained was fed to a twin screwextruder (TEM-50B, manufactured by Toshiba Kikai K.K.) preset at acylinder temperature of 150° C. and pelletized at a rotational speed of100 rpm.

EXAMPLES 8 to 12

The operation was conducted in the same manner as in Example 1 exceptthat the blend composition was as identified in Table 4.

COMPARATIVE EXAMPLES 2 to 6

The operation was conducted in the same manner as in Example 1 exceptthat the blend composition was as shown in Table 4.

EXAMPLE 13

The composition obtained in Example 1 was kneaded by 12 inch twin rollspreset at a surface temperature of 180° C. to obtain a sheet, which wassubjected to a pelletizer to obtain angular pellets. From such pellets,glass run channels and weather strippings as automobile parts and tubeswere prepared by means of a 40 mm extruder, and the practical physicalproperties were measured. The results are shown in Table 3.

COMPARATIVE EXAMPLE 7

From the composition prepared by the process of Comparative Example 1,glass channels, weather strippings and tubes were prepared in the samemanner as in Example 13, and the practical physical properties weremeasured. The results are shown in Table 3.

In the Examples and Comparative Examples, the tensile strength (T_(B)),the elongation (E_(B)), the tear strength (TR) and the compression set(C_(s)) were measured in accordance with the following methods:

Tensile strength (T_(B)): In accordance with JIS K-6723.

Elongation (E_(B)): In accordance with JIS K-6723.

Tear strength (TR): In accordance with JIS K-6301, method B.

Compression set (C_(s)): In accordance with JIS K-6301 at 70° C. for 22hours under a compression rate of 25%.

                  TABLE                                                           ______________________________________                                                    Tested       Example  Comparative                                 Molded products                                                                           properties   13       Example 7                                   ______________________________________                                        Glass channels                                                                            Compression  41       65                                                      set (%)                                                           Weather strippings                                                                        Compression  45       55                                                      set (%)                                                           Tubes       Hydraulic    10.5     6.1                                                     pressure                                                                      resistance                                                                    (or water leaking                                                             pressure (kg/cm.sup.2)                                            ______________________________________                                    

It is evident that with respect to each of the tested properties,Example 13 is superior to Comparative Example 7.

The testing methods were as follows.

(1) Glass run channels

As diagrammatically illustrated by a cross sectional view in FIG. 1, aglass run channel product 1 was prepared by extrusion molding by meansof a 40 mm extruder. The glass channel product 1 having a length ofabout 20 cm thus obtained was put into a casing 2 made of metal as shownin FIG. 2, and a spacer 3 made of glass having a thickness (S) of 5 mmwas inserted. This assembly was introduced into a Geer oven tester, leftto stand at 90° C. for 24 hours and then withdrawn, and the spacer wasimmediately removed. 30 Minutes later, the residual strain x mm wasmeasured as shown in FIG. 4.

The compression set (%) was calculated by the following equation.##EQU1## where x is the residual strain, and S is the thickness of thespacer.

(2) Tubes

A tube having an internal diameter of about 4 mm and an outer diameterof about 7.5 mm was prepared by extrusion molding by means of a 40 mmextruder. To one end of the tube having a length of about 50 cm thusobtained, a tubular connector having an outer diameter of 8 mm wasinserted for a insertion length of 14 mm, and the other end of the tubewas closed. The assembly was subjected to heat treatment at 100° C. for8 hours in a Geer oven tester. Then, a hydraulic pump was connected tothe tubular connector, and the pressure was increased at a rate of from15 to 25 kg/cm² /min, whereby the pressure at the time when waterleakage started was measured, and this pressure was taken as thehydraulic pressure resistance.

(3) Weather strippings

As illustrated by a cross section in FIG. 5, a weather stripping product4 was prepared by extrusion molding by means of a 40 mm extruder. Themolded product 4 was secured to a sample holder plate 5 by e.g. anadhesive, for measuring the compression set. The assembly was set in thedevice for measuring the compressing set as shown in FIG. 6 with aspacer 6 to determine the height x₂ so that the compression rate of themolded product i.e. the test sample would be 30%, as shown in FIG.6. InFIG. 6, reference numeral 7 indicates a compressing plate, numeral 8indicates a bolt and numeral 9 indicates a nut.

The assembly was introduced into a Geer oven tester, left at 90° C. for24 hours and then withdrawn. The spacer was immediately removed, and 30minutes later, the height of the test sample was measured. Thecompression set was calculated by the following equation. ##EQU2## wherex₀ is the initial height of the test sample, X₁ is the height of thetest sample after the test, and x₂ is the height of the spacer or theheight of the test sample under compression.

In the following Tables, "parts" means "parts by weight".

                                      TABLE 4                                     __________________________________________________________________________                  Example                                                                       1  2  3  4  5  6  7  8  9  10 11 12                             __________________________________________________________________________    Vinyl chloride resin (parts)                                                                100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                            Average degree of                                                             polymerization 1700                                                           NBR (parts)                                                                   Chemigum P8B1A2                                                                             50 50 50 50 50    50    50 280                                                                              50 100                            JSR PN-30A                   50    20                                         Plasticizer (parts)                                                                         90 90 90 90 90 90 90 90 90 50 30 190                            DOP                                                                           Additives (parts)                                                             Ba--Zn stabilizer                                                                           3  3  3  3  3  3  3  3  3  3  3  3                              Epoxidized soybean oil                                                                      3  3  3  3  3  3  3  3  3  3  3  3                              Filler (parts)                                                                Calcium carbonate                                                                           50 50 50 50                                                     Carbon black              50 50 50 50 50 50 20 50                             Curing agent (parts)                                                          Sulfur        1.5                                                                              1.5                                                                              1.5   1.5                                                                              1.5                                                                              1.5                                                                              1.5                                                                              1.5                                                                              1.5                                                                              1.5                                                                              1.5                            Nocceler CZ   1           1  1  1  1  1  1  1  1                              Zinc oxide    5  5  5     5  5  5  5  5  5  5  5                              Perhexa 3M-40          1                                                      Triallyl isocyanurate  5                                                      Tetramethylthiuram disulfide                                                                   1                                                            Dibenzothiazyl disulfide                                                                          2                                                         Kneader       PK*                                                                              PK*                                                                              PK*                                                                              PK*                                                                              PK*                                                                              PK*                                                                              TE*                                                                              PK*                                                                              PK*                                                                              PK*                                                                              PK*                                                                              PK*                            Jacket temperature (°C.)                                                             150                                                                              150                                                                              150                                                                              150                                                                              150                                                                              150                                                                              150                                                                              150                                                                              150                                                                              150                                                                              150                                                                              150                            Resin temperature (°C.)                                                              175                                                                              175                                                                              173                                                                              173                                                                              190                                                                              190                                                                              200                                                                              191                                                                              160                                                                              180                                                                              200                                                                              180                            Processability                                                                              ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                                                                    ◯                  T.sub.B (kg/cm.sup.2)                                                                       170                                                                              165                                                                              172                                                                              175                                                                              180                                                                              175                                                                              158                                                                              153                                                                              150                                                                              120                                                                              180                                                                              125                            E.sub.B (%)   300                                                                              330                                                                              310                                                                              350                                                                              320                                                                              450                                                                              350                                                                              300                                                                              320                                                                              305                                                                              280                                                                              310                            TR (kg/cm)    31 33 31 35 36 38 37 30 29 32 50 35                             C.sub.s (%)   32 32 32 30 30 38 35 39 38 22 35 35                             __________________________________________________________________________                              Comparative Example                                                             1  2  3  4  5  6                                  __________________________________________________________________________                  Vinyl chloride resin (parts)                                                                100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100                                              Average degree of                                                             polymerization 1700                                                           NBR (parts)                                                                   Chemigum P8B1A2                                                                             50 50 50 350                                                                              50 50                                               JSR PN-30A                                                                    Plasticizer (parts)                                                                         90 20 250                                                                              90 90 90                                               DOP                                                                           Additives (parts)                                                             Ba--Zn stabilizer                                                                           3  3  3  3  3  3                                                Epoxidized soybean oil                                                                      3  3  3  3  3  3                                                Filler (parts)                                                                Calcium carbonate                                                                           50                                                              Carbon black        50 50 50 50                                               Curing agent (parts)                                                          Sulfur           1.5                                                                              1.5                                                                              1.5                                                                              1.5                                                                              1.5                                              Nocceler CZ      1  1  1  1  1                                                Zinc oxide       5  5  5  5  5                                                Perhexa 3M-40                                                                 Triallyl isocyanurate                                                         Tetramethylthiuram disulfide                                                  Dibenzothiazyl disulfide                                                      Kneader       PK*                                                                              PK*                                                                              PK*                                                                              PK*                                                                              PK*                                                                              PK*                                              Jacket temperature (°C.)                                                             150                                                                              150                                                                              150                                                                              150                                                                              100                                                                              190                                              Resin temperature (°C.)                                                              183                                                                              200                                                                              192                                                                              175                                                                              120                                                                              230                                              Processability                                                                T.sub.B (kg/cm.sup.2)                                                                       ◯                                                                    X  ◯                                                                    X  X  Decomposed                                       E.sub.B (%)   280                                                                              200                                                                              250                                                                              150                                                                              230                                                                              (not                                             TR (kg/cm)    18 40 19 12 25 measurable)                                      C.sub.s (%)   54 45 45 25 45                                    __________________________________________________________________________     *PK: Pressure kneader                                                         **TE: twin extruder (rotation: same direction)                                ◯: Excellent                                                      X: Poor                                                                  

Vinyl chloride resin having an average degree of polymerization of 1700:Denka Vinyl SH-170, manufactured by Denki Kagaku Kogyo Kabushiki Kaisha

Chemigum P8B1A2: Powdery NBR, mooney viscosity: 79, bound acrylonitrile:33%, partially pre-crosslinked type, manufactured by Good Year Co.

JSR PN-30A: Powdery NBR, mooney viscosity: 56, bound acryronitrile: 35%,non-cross-linked type, Japan Synthetic Rubber Co., Ltd.

DOP: Di-2-ethylhexyl phthalate, W520, manufactured by Dainippon Ink K.K.

Ba-Zn stabilizer: Ba-Zn fatty acid salt composite stabilizer, BZ-100J,manufactured by Katsuta Kako K. K.

Epoxidized soybean oil: Adekacizer O-130P, manufactured by Adeka ArgusChemical Co.

Calcium carbonate: NS-400, manufactured by Nitto Funka Kogyo K. K.

Carbon black: Diablack H, manufactured by Mitsubishi Kasei Corporation

Sulfur: Powder sulfur, manufactured by Hosoi Kagaku Kogyo K. K.

Nocceler CZ: N-cyclohexyl-2-benzothiazyl sulfeneamide, manufactured byOuchi Shinkosha

Zinc oxide: ZINCA 10, manufactured by Sakai Kagaku Kogyo K. K.

Perhexa 3M-40: Peroxide,1,1-bis-tert-butylperoxy-3,3,5-trimethylcyclohexane (purity: 40% byweight), manufactured by Nippon Fat and Oil Co., Ltd.

Triallyl isocyanurate: manufactured by Kurogane Kasei K. K.

Tetramethylthiuram disulfide: Nocceler TT, manufactured by OuchiShinkosha

Dibenzothiazyl disulfide: Nocceler DM, manufactured by Ouchi Shinkosha

We claim:
 1. A thermoplastic elastomer composition obtained by a processconsisting essentially of simultaneously kneading and curing at atemperature from 140°-220° C. a mixture comprising 100 parts by weightof vinyl chloride resin, from 20-300 parts by weight of a powdery andpartially pre-crosslinked copolymer of butadiene and acrylonitrile, from25-200 parts by weight of a plasticizer, from 10-200 parts by weight ofa filler and curing agent for the rubber which cures at a temperatureranging from 140°-220° C., said composition being meltable by a roll setat a temperature of 190° C.
 2. The thermoplastic elastomer compositionaccording to claim 1, wherein said partially pre-crosslinked copolymerof butadiene and acrylonitrile contains from 20 to 45% of a boundacrylonitrile.
 3. The thermoplastic elastomer composition according toclaim 1 wherein said plasticizer is a member selected from the groupconsisting of phthalic acid esters, trimellitic acid esters,pyromellitic acid esters, aliphatic dibasic acid esters, glycol esters,fatty acid esters, phosphoric acid esters and citric acid esters.
 4. Thethermoplastic elastomer composition according to claim 1 wherein saidcuring agent is sulfur, zinc oxide, magnesium oxide, an organicperoxide, triazinethiol, a benzothiazole sulfenamide accelerator,benozthiazyl disulfide, a phenol resin, m-phenylene bismaleimide,thiuram disulfide or dipentamethylene thiuram hexasulfide.
 5. Thethermoplastic elastomer composition according to claim 1, wherein theamount of said curing agent in the composition is at least 0.1 point byweight per 100 parts by weight of the total amount of vinyl chlorideresin and partially pre-crosslinked copolymer of butadiene andacrylonitrile.
 6. The thermoplastic elastomer composition according toclaim 1, wherein the filler is carbon black and/or calcium carbonate. 7.The thermoplastic elastomer composition according to claim 1, whereinthe curing agent is a peroxide or a phenol resin.
 8. A thermoplasticelastomer composition obtained by a process consisting essentially ofsimultaneously kneading and curing at a temperature from 140°-200° C., amixture which comprises 100 parts by weight of a vinyl chloride resin,from 20-300 parts by weight of a powdery and partially pre-crosslinkedcopolymer of butadiene and acrylonitrile, from 25-200 parts by weight ofa plasticizer, from 10-200 parts by weight of a filler and a curingagent for the rubber which cures the rubber at a temperature of from140°-220° C., said composition having a tensile strength of at least 120kg/cm² and a rate of compression set of not greater than 40% after beingcompressed at a compression rate of 25% at a temperature of 70° C. overa period of 22 hours and said composition being meltable by a roll setat a temperature of 190° C.